Compositional dependence of g-factor and damping constant of (Gd100-xREx)FeCo alloy films (RE = Yb, Tm, Er)

Time domain magnetization dynamics of (Gd100-xREx)FeCo (RE = Yb, Tm, Er) alloy films with various compositions were measured by pump-probe method using a high energy ultra short pulse fiber laser, and their g-factors and damping constants were estimated. The g-factor of GdFeCo became large near the angular moment compensation point CA, which is qualitatively consistent with the simple mean field model. On the other hand, the damping constants took a maximum near magnetization compensation point, which is not described by the mean field model. Substitution of Tm or Er for Gd results in the significant increase of damping constant; (Gd90Tm10)FeCo and (Gd90Er10)FeCo exhibit roughly 3-6 times large damping constant compared to GdFeCo, while (Gd90Yb10)FeCo has almost the same damping constant as GdFeCo. This means that the damping constant is significantly modified by the orbital moment of RE atoms.